The subject matter herein relates generally to cable assemblies and, more particularly, to cable assemblies configured to communicate data signals.
Some known cable assemblies include two or more conductors that extend along the length of the cable assembly. The conductors may be arranged in pairs and configured to communicate a differential pair signal along the length of the cable assembly. In order to reduce electromagnetic interference caused by communication of the differential pair signals along the conductors, the conductors may be twisted around one another at a twist rate. For example, the conductors may be twisted around a longitudinal axis of the cable assembly such that each conductor encircles the longitudinal axis multiple times along the length of the cable assembly. Twisting the conductors about one another may cancel out both external and internal electromagnetic interference in the conductors that is caused by an external source.
The conductors may be enclosed in insulative jackets, which are then encased in a shield. The shield may be a tape that is wound around the conductors and the jackets. The shield includes a conductive material and is electrically coupled with an electric ground reference to shield the conductors from electromagnetic interference. In some known cable assemblies, a drain wire is located within the shield along the length of the cable assembly. The drain wire is electrically joined with the shield and with the ground reference to communicate the electromagnetic interference to the ground reference. In order to shield the conductors from electromagnetic interference, typically the drain wire is carefully located between the conductors, or is aligned with the midpoint between central axes of the conductors in a direction extending perpendicular to the longitudinal axis of the cable assembly and perpendicular to the lateral distance between the central axes of the conductors. Displacing the drain wire off-center from this midpoint of the conductors may reduce the effectiveness of the drain wire and shield in shielding the conductors from electromagnetic interference.
Additionally, some known cable assemblies include a shield that is helically wound around the conductors and insulative jackets as a tape. The wrapping of the tape around the conductors and insulative jackets may result in gaps between adjacent windings of the tape. For example, the tape may not be wrapped in such a way that the tape overlaps itself as the tape is wound around the conductors and insulative jackets along the length of the cable assembly. The gaps may cause non-linear performance of the cable assemblies in the relationship between frequency domain of the signals communicated using the cable assemblies and power losses in the signals. For example, the gaps may cause significantly larger losses in one or more bands or subsets of frequencies relative to the losses incurred at other frequencies or frequency bands. Moreover, the power loss in low frequency signals communicated using some known cable assemblies may be relatively large.
Some known cable assemblies position the conductors too close to the shields of the assemblies. Positioning the conductors too close to the shield may result in electrical coupling between the conductors and shield. The coupling may cause a time skew in the signals communicated using the conductors. The time delay skew includes the difference in propagation delay along the length of the conductors between the faster and slower of the two conductors in the differential pair. An increase in the time delay skew can adversely impact the integrity of the signal.
There is still a need for a cable assembly that reduces electromagnetic interference leakage both into and out from the cable assembly.